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and serve the whole

and serve the whole building except car parks and data centre equipment because their inclusion would distort the BEI. The gross floor area shall be the gross area of occupied space excluding car park areas and the data centre room, which corresponds with the exclusion of energy consumption for these areas. It should also be noted that this BEI method is not applicable to buildings without much airconditioning in building floor spaces, such as for residential buildings. For the purpose of this study, it is suggested to set the minimum air-conditioned space to be at least 50 percent of the gross floor area for a meaningful comparison of BEI in buildings. Another aspect that will influence the BEI values is building categories and operational hours. For example, BEI for office buildings will differ from that of shopping malls, which again will differ from that of hotels and hospitals. In the absence of proper surveyed data in Cambodia and for the purpose of having some values for discussion purposes, the table below provides typical values, which are based on the green building benchmark values in Malaysia. It is not suggested that Cambodia should adopt the benchmarking values listed below. The intention of listing these values is to illustrate that BEI values can be determined if there are sufficient quality data on buildings. From the energy consumption survey data obtained for the building sector in Cambodia in the recent exercise, it was not possible to establish similar BEI benchmarking values. Table A4.1 Typical Minimum Building Energy Intensity Benchmarking Values for Green Buildings Building Category Typical Operational Hours Office 52 hours/week 150 Retail and Mall 84 hours/week 200 BEI (minimum values to be considered energy efficient) (kWh/m 2 /yr) 350 (incl. high energy intensity outlets) 24 hours / 7 days 200 290 Hotel week (3-star & below) (4-star & above) 24 hours / 7 days 290 Hospital 200 week (incl. major clinical services) Source: Green Building Index (GBI), GBI Tools, Malaysia. 3. Strategies to Achieve Energy Efficiency The common approach to achieve energy efficiency in buildings is to improve efficiency in lighting and air-conditioning systems. However, for a hot and humid climate like in Cambodia, it is important to firstly adopt a passive design strategy before considering an active design strategy in order to attain a holistic approach to energy efficiency in buildings. 78 | Annex 4

3.1 Passive Design Strategy For a hot and humid climate, all buildings have the primary function of providing an internal environment with thermal comfort, which is desirable for the purpose of occupancy in buildings. Therefore, understanding weather conditions will offer opportunities to minimise solar heat gains, which will lead to saving capital costs due to the reduction in the capacity of air-conditioning equipment and ultimately saving energy costs in the operation of buildings. The primary objective in a passive design strategy is to minimise solar thermal heat gains and some examples of the key elements to be considered in this strategy are as follows: a) Building orientation with the longer building axis facing North–South so that the narrow ends of the building face East–West. b) Building facades that provide shading for windows. c) Fenestrations (windows) that provide low thermal transmittance and an effective shading coefficient of glazing used in the fenestration system. d) Building and insulating materials that provide low thermal transmittance of the opaque walls and roofs. e) Strategic landscaping that provides shading from the sun, shielding from heat reflection in the surrounding spaces, and the creation of a cooler microclimate around the building. f) Daylighting design that captures the natural daylight to reduce the need for artificial lighting. g) Natural ventilation that makes use of the natural forces of wind and buoyancy to deliver sufficient fresh air and air change to ventilate enclosed spaces without the need to rely on air conditioning. h) Measures to prevent air leakage as uncontrolled mixing of outside air with air-conditioned space requires more energy to remove moisture and heat gain contributed by air leakage. 3.2 Active Design Strategy Having minimised solar heat gain and having maximised the capture of daylight and natural ventilation, an active design strategy will play a key role to complete the achievement of energy efficiency in buildings. The extent of energy efficiency in active systems often depends on budget allocations. If budget permits, sophisticated energy management and lighting control systems may be considered. The minimum approach in an active design strategy is to cover systems that consume higher shares of energy, i.e. airconditioning systems and lighting. Annex 4 | 79